Despite recent advances in the treatment and prevention of cardiovascular disease, stroke remains the third leading cause of death and a leading cause of serious, long-term disability in US. Therapeutic strategies aimed at minimizing the deleterious effects of ischemia on neurons once stroke takes place are still lacking, and clinical trials using neuroprotective agents have largely failed. We uncovered an endogenous mechanism of neuroprotection, whereby neurons respond to ischemia by increasing the number of peroxisomes, highly adaptable small organelles that contribute to neuronal survival by enhancing neuronal cell antioxidant capacity and the ability to cope with metabolic stress during ischemia-reperfusion. The proposed project will use both in vivo and in vitro models of ischemic neural injury to determine if peroxisomal proliferation is increased in neurons after ischemia by the translocation to peroxisomes of an otherwise cytosolic enzyme called soluble epoxide hydrolase (sEH). Aim 1 will determine if sEH translocation requires binding of its peroxisome-targeting signal-1 (PTS-1), located on the C-terminal, to the peroxisomal shuttle protein peroxin 5 (PEX5). Aim 2 will determine if sEH translocation contributes to peroxisomal proliferation, which plays a neuroprotective role after cerebral ischemia. Aim 3 will determine if increased peroxisomal density after cerebral ischemia is mediated though a dual action of sEH to promote peroxisomal biogenesis and suppress peroxisomal degradation. The proposed research is highly significant and innovative both technically and conceptually. Peroxisomal biogenesis has not been previously described in brain after cerebral ischemia, and a role for sEH in this process has not been investigated. If confirmed, the proposed studies will pave the way for a new line of research focusing on peroxisomal biogenesis after stroke, and may lead to the development of novel therapeutic agents for stroke based on promoting peroxisomal translocation of sEH and enhancing the endogenous neuroprotective response to increase peroxisomal biogenesis and prevent their degradation.